Rating of Perceived Exertion
An extremely useful method of gauging intensity is your rate of perceived exertion. A scale called the Borg scale I find very helpful and easy to use. It begins at 6 and maxes out at 20. Why not just 1-10? In general, the Borg scale was designed to correspond to 1/10th of the HR at that level. In other words, a resting HR of 60, and a max HR of 200. You know from the discussion on HR that such a strict HR scale is not appropriate for everyone, but I find it to be a useful gauge for correlating your perceived exertion with your own HRs. Using it is simple; you just pick the level that corresponds to your exertion level.
Using RPE along with your Heart Rate
With practice and objective use, especially if you combine it with a HR monitor for awhile, you will become very sensitive to your relative training zone based solely on your exertion level. Although your daily energy levels will fluctuate due to sleep, nutrition, hydration and motivation, an objective determination of RPE should remain fairly constant. Note what RPE descriptions are associated with the HR zones determined above. If you are training your aerobic engine, your RPE should remain around 9-11. This will seem ridiculously easy and slow for some people. It requires a small amount of faith that you are actually improving your aerobic fitness while training in these zones, and if you stick with it in an organized, structured fashion, you will see improvements over time. Remember, a better aerobic engine means you will last longer, be fresher, recover faster and have more reserves for short bursts of energy.
Download a color coded PDF file by clicking on the text: Rating of Perceived Exertion
Below is the same chart.